I guess tires do harden with age

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Been thinking about what to do with some 6 year old snow tires off an older car. [Yes I know, they're "too old".] Dawned on me this morning, maybe they'd fit my car? Not sure yet. But at some point, during some pandemic spree buying, I picked up a tire durometer, and, what the heck, let's see what some numbers are.

Garage door opener says the interior wall is 46F in the garage today, and everything's been in there for a couple of days. So I'll assume the same temperature for all (snows are stacked next to the car).

Six year old snows (General Artic something).
snow.jpg


Some RT43's that I had put on in August, about 8kmiles ago.
allseason.jpg


Not sure I got into nice wide areas of the blocks (darn siping! oh wait, that's a good feature! :) ) but those are a couple of spot checks. I should probably start a logbook somewhere, age, temperature and measurements.

Maybe I'll not bother with swapping, the new tires might be softer...

In other news, just realized, I must have forgotten to rotate these new tires, I can feel the feathering start. Great... so much for hoping alignment and new struts would fix that problem.

Anyhow. Random I know, but it's Saturday.
1670687040280.jpg
 
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I wonder what the 8 y.o. Michelin XZX tires on my 1975 Civic would have read on that gauge.
They had ~80,000 miles and plenty of tread left.
I made a panic stop when a truck ran a stop sign.
No collision, but my little go-cart of a car swapped ends in the blink of an eye.
That's the day I learned there's more to good tires than tread depth. :eek:
 
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1) How do you know it's not just the outer 0.1 mm of the rubber that is exposed to air that gets hard?
2) How do you quantify those reading between brands of tires?
3) How do you determine what is a good or bad reading? Wouldn't a harder tire last longer?
 
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The chemical compounds that make a tires soft are call plasticizers which are low molecular weight and volatile.

You do loose over time leading to stiff tires just like me.
 
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My winter tires are 13 years old. I really need new ones, but I'm hoping this is the last winter with this car, so I'm hesitating getting new ones.
 

JTK

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I had no idea a durometer existed. So zero on the dial is basically mush and 100 is rock hard?

I hear you on snow tire age. It can creep up on you. I'll have to look at the year on the firestone winterforces we run on the 2015 Nissan Versa, but I'm pretty sure they are from 2015. There's little/no wear on them after ~8 winters, but the car is relatively low mileage at ~69K miles.
 

AZjeff

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@JTK, no that's not how the scale works. There are different hardness scales, A,B,C,D etc to give better resolution so you don't use the same durometer to measure seat foam and hockey pucks.

Measuring different tires and different brands will show the difference in hardness of those examples but without knowing the starting hardness pretty much impossible to make valid conclusions.
 
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I have a tire durometer also. It's fun to play with!

I purchased a Bridgestone rear motorcycle tire with dual compounds for my SV1000s. I measured the compounds after noticing some odd and very rapid wear, and found they were switched, with the soft compound in the middle and harder compounds on the edges. I wrote Bridgestone about this and they offered no help.

The center balled up like a slick right away, and stayed like that for the very short life of the tire. I think it made it about 800 miles. I ride slow, and easy. So the durometer confirmed the mistake.

The replacement tire (different brand) was soooooo much better.
 

supton

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1) How do you know it's not just the outer 0.1 mm of the rubber that is exposed to air that gets hard?
2) How do you quantify those reading between brands of tires?
3) How do you determine what is a good or bad reading? Wouldn't a harder tire last longer?
1. no idea, but its that outer 0.1mm touching asphalt, so that is the important part
2. I would assume you can, but the temperature has to be the same. But it is possible for different tires to act differently. big thing is , how much does one particular tire changes as it ages?
3. harder should last longer, but it may lead to less than optimal operation under adverse conditions. think sudden stops (see above) or traction in cold weather on ice.
 

AZjeff

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The durometer pushes a prong ito the rubber, if it's just the outer 0.1mm that hardens it will have very little effect on the measurement

It's also good to take the reading at the same time interval, it will read differently at 1 second compared to 10 seconds as the prong is slowly pushed into the material the reading decreases. I'd take 8-10 readings around a tire and average. Used durometers a lot at work.
 
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Yesterday I removed a tire from a wheel that had been mounted at least 20 years, probably closer to 30. I had to saw it almost completely through in quarters to get it to flex enough to break the bead. You don’t have to convince me tires get hard as they age.
 
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I had no idea a durometer existed. So zero on the dial is basically mush and 100 is rock hard?

There are several durometer hardness scales.

The Shore 00 Hardness Scale is for very soft polymers and rubbers.

The Shore A Hardness Scale measures the hardness of flexible materials and goes from very soft and flexible to hard and almost rigid. That's the correct scale for checking tire hardness and that's why there's an A on the gauge scale in the above pictures.

The Shore D Hardness Scale measures the hardness of hard rubbers, semi-rigid plastics and hard plastics.

Mohs Scale is used for determining the hardness or rather the scratch resistance of minerals. and goes from 1 (talc) to 10 (diamond). Then there are also Vickers and Rockwell that measure indentation.
 
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1) How do you know it's not just the outer 0.1 mm of the rubber that is exposed to air that gets hard?
2) How do you quantify those reading between brands of tires?
3) How do you determine what is a good or bad reading? Wouldn't a harder tire last longer?
Rubber has a lifespan. The moment it’s vulcanized it starts to decay. Any tire older than 8 years is past its life expectancy no matter how much tread is left. Either that or tire makers just publish that information to get people to buy tires more often.
Oh wait the life span of tires is from the National highway safety Administration. Eight years old new buy new tires. And don’t buy used ones for the same reason you don’t buy underwear from a second hand store.
 
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